Hi Mabula – way back when (early 90s), I wrote a database application when we were running a real estate multiple listing system and charging monthly “subscriber” fees to each of the real estate agents. I was concerned about them sharing the application and not paying my monthly fees. The solution I had at the time was to tie the licensing to a single computer. Basically, when they started the app, I had it run a separate program that grabbed (if I recall) some serial number from the CPU. The first time the program ran, it wrote a config file that had this info. Subsequent times verified the system CPU serial number and compared it to the config. In this way, the application could only be run on one computer.
What you might want to think about is having your regular APP version and then having a separate “requires no internet connection” version. The difference would be that the requires no internet version could only be run on one computer. It would require additional work on your part, but when someone wanted this version of the app, you would first send them some little program that would parse some hardware specific info (maybe a mac address) and generate a file to send to you. The user would send back that file to you, and then you could send them a version of APP that checked for that hardware specific identifier. In this way, the user couldn’t share the program, but also wouldn’t require an internet connection for authenticity check.
It’s a bit more of a pain, and the vast majority of people would not require this version (they could easily accommodate the internet connected version). For the relatively small percentage that want to run it on a never connected computer, you would give them this version (you could even allow them torun it on the 2 or 3 computers by having them send you the hardware specific file for 2 or 3 computers). They’d need to understand that any computer change would necessitate them contacting you for an updated version. And, you’d need to figure some way for distributing updates that left their config file intact. But, it might be an adequate compromise solution.